Siege Engines Rules:

Siloflex must meet the following standards: for pipe that is black in color, it must be manufactured to ASTM D2239 or D2737; be made from PE3408
or PE3608; be sized 1"ID (2.5cm) if D2239 or 1-1/4"OD (3.2cm) if D2737; and have a SIDR rating of 15 or lower or have a SODR rating of 17 or lower.

For pipe that is yellow in color, it must be manufactured to ASTM D2513; made from PE2406 or PE2708; be 1"IPS (2.5cm); and have an SDR of 11. (Please note that shafts made from yellow Siloflex may not be covered with tape, and the markings must be visible.)